Listeria monocytogenesin Multiple Habitats and Host Populations: Review of Available Data for Mathematical Modeling

Abstract

Listeria monocytogenes has the ability to survive and multiply in diverse habitats and to cause infection in a variety of animal species and humans. We evaluated the literature on survival and multiplication within and transmission among multiple host populations and habitats, including man, sewage, general environment (soil, water, and vegetation), silage (fermented plant material), animals (including wild and domestic animals), and food processing plants. The available knowledge on L. monocytogenes transmission dynamics was translated into the key process nodes of interrelated host- and habitat-specific mathematical models, providing a starting framework for future modeling work and the ultimate development of a system-wide model for evaluation of its transmission, and strategies to reduce human exposure. Because of the ability of L. monocytogenes to survive and multiply in many habitats and hosts, and the number of possible transmission routes, it is highly unlikely that it could be eradicated from any habitat or host, including man. However, L. monocytogenes load within and transmission among habitats and host populations could probably be reduced. Based on the published information, we hypothesize that three recent anthropogenic practices increase the load within and transmission among reviewed habitats and host populations: extended refrigerated storage of ready-to-eat foods allowing L. monocytogenes growth in foods that are contaminated during production or subsequent handling; feeding domestic ruminants with silage often contaminated with L. monocytogenes; and dispersal of contaminated products of sewage treatment to agricultural fields and waters. Future mathematical modeling work could test how much the reduction of L. monocytogenes load and transmission in hosts and habitats associated with these anthropogenic practices would reduce human exposure and consequently human listeriosis.

Review. Dairy farm management and production practices associated with the presence of Listeria monocytogenes in raw milk and beef

“…However, under aerobic conditions, sufficient fermentation to drop the pH to below 4.5 may not occur, or growth of aerobic microorganisms such as yeasts and moulds may be initiated; this tends to increase the silage pH to favourable levels for the growth of L. monocytogenes (Ivanek et al, 2006).…”

“…The duration of faecal shedding is not well understood, but it could be dependant on both silage contamination and exposure to stress (Fenlon et al, 1996;Ivanek et al, 2006). Seasonal variations in faecal shedding could be associated with increased silage feeding during the cold season (Nightingale et al, 2005;Ryser, 2007).…”

Outdoor environment as a source of Listeria monocytogenes in food chain

“…l. monocytogenes can also be isolated from the surface and underground waters, improperly fermented silage, sewage sludge, slaughter wastes, animal and human faeces, foodstuffs, and food industry plants (Farber & Peterkin 1991;Ivanek et al 2006). In both animals and susceptible humans, l. monocytogenes causes serious invasive disease.…”

“…In ruminants, the disease manifests itself primarily by neurological symptoms or abortion, and very uncommonly, by mastitis. However, as a rule, l. monocytogenes passes asymptomatically through the gastrointestinal tract to be excreted in faeces (Ivanek et al 2006;Esteban et al 2009). Fecal contamination of soil, vegetation, and surface water is the major source of l. monocytogenes in primary food production (Ivanek et al 2006).…”

PRESENCE OF Listeria monocytogenes IN HEALTHY CATTLE AT SLAUGHTERING: FIRST RESULTS

“…Gli insilati costituiscono una delle principali fonti di contaminazione per gli animali in allevamento, soprattutto nel caso in cui siano di cattiva qualità (pH >5) (13).…”